HI, My eg has been pinging/knocking very loudly when i first start the engine, its revs to about 1800 RPM with or without A/C on. FOr the first 3-5 mintues taht I drive it pings ,sounds like knocking but it always goes away after those 5 minutes! Im guessing its my intake manifold or something maybe dirty but could it be internal , does anyone know what is wrong with my engine??? or had similar problem with their engine?